الفهرس 
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Abstract
Objective: To evaluate the effect of long term exposure to simulated gastric acid on surface roughness and color change of different ceramic systems. Materials and methods: A total 50 discs were divided into five groups (n= 10) according to the type of ceramic system: Zolid FX, IPS e.max CAD, Vita Mark II, Vita Enamic and Vita Suprinity. All discs were immersed in (0.06 M) HCl with pH 1.2 for 144 hours at 37oC. Surface topographical changes of the discs were measured with atomic force microscope and scanning electron microscope, while the color changes were measured with a spectrophotometer and the mean values of color difference (∆E) were calculated. The data were analyzed with One-way ANOVA followed by post-hoc tukey’s test for pair-wise comparison between the groups.
Results: There was significant difference in ΔRa values (p<0.05) between all groups. The mean values of color difference (∆E) within a range from 2.64 to 5.31. Zolid FX showed the lowest value, and Vita Enamic had the highest value. Conclusions : The simulated gastric acid has direct effect on surface topography and the final color of tested ceramic materials.